An Air Data System (“ADS”) provides sensed telemetry informing pilots, navigators or Vehicle Management System computers of air parameter(s) affecting aircraft stability. These air parameters include, for example, air speed, air temperature and air pressure, each being useful for navigation and flight control. The ADS exists in many forms, for example, as mechanical, opto-mechanical or opto-electronic devices.
An Optical Air Data System (“OADS”) uses light to determine parameters of air speed. The OADS transmits light pulses into the atmosphere and receives light that aerosols reflect or “backscatter” towards the aircraft. Aerosols are fine solids and/or liquid particles suspended in air or other gases. The OADS may also measure the Doppler effect by receiving backscattered light and measuring its return frequency to determine speed. Certain prior art OADSs rely on scattered light that is unpredictable because of aerosol distributions that vary significantly with altitude and cloud content. In addition, some regions of the atmosphere contain too few aerosols to enable reliable air data measurements, and such an OADS cannot determine air temperature or air pressure.
Ground-based air data measurements can also be of interest in other applications such as wind measurements for weather monitoring, weather prediction and traffic alerts.
Wind conditions near airports and on approach paths to airports can be of great interest to pilots. In particular, improved detection and measurement of wind shear, updraft, downdraft, and microburst conditions has been of interest since a microburst was blamed for the demise of a Lockheed L-1011 trying to land at Dallas in 1985. Aircraft are particularly sensitive to such wind conditions during the critical flight phases of takeoff and landing; it is desirable to equip airports with devices for detecting such conditions so that destruction of aircraft and death of crew and passengers can be avoided.
Wind conditions are often measured at more than one point on an airport in an attempt to detect potentially harmful wind conditions. Since wind shear is characterized by a difference in wind speeds and directions with altitude, it is also desirable to measure wind conditions at several altitudes and not just near the surface.
Tax and other incentives enacted by the United States and several states have increased interest in obtaining electric power from renewable energy sources, including wind power systems. Detailed measurements of wind speed, air temperature, air turbulence, and similar information at the surface and at altitudes within a few hundred meters of the surface are of use in evaluating locations for wind power systems. Further, realtime measurements of wind conditions, turbulence, and temperature at the surface and at altitude may be of use in controlling wind power systems and in predicting updrafts and microbursts to help protect such systems from adverse conditions.